Electric control device



Dec. 10, 1946.

M. F. JONES ET AL ELECTRIC CONTROL DEVICE Filed Dec. 11, 1944 INVENTOR 2Maur/ce f? Jones and fiue/ C. fines.

WITNESSES: I m k J 6% u...

BY 47 M8.

ATTORNEY Patented Dec. 10, 1946 UNITED STATES PATENT OFFICE ELECTRICCQNTROL DEVICE Maurice F. Jones, Pittsburgh, and Ruel C. Jones, ForestHills, Pa., assignors to Westinghouse Electric Corporation, EastPittsburgh, Pa, a corporation of Pennsylvania Application December 11,1944, Serial No. 567,636

6 Claims. 1

Our invention relates to electric control devices and has for itsgeneral object to provide control means which perform a controloperation when the rate of acceleration or deceleration of a 1'0- tatingmachine part reaches a given value.

It is also an object of the invention to devise an acceleration ordeceleration responsive switch which permits readily an adjustment,calibration or change of the critical value of the rate of speed changeat which the switching operation is supposed to take place.

Another object, allied to the one just mentioned, is to render a switch,of the type referred to, capable of being separately adjusted forresponse to acceleration and deceleration, respectively, so that thecorresponding critical values may be chosen differently if desired.

A further object of our invention is to provide a switch, as mentionedabove, in which the response to rate of change in speed is due to theoccurrence of relative motion between a driven rotatable member and arotatable floating mass or flywheel member and wherein such relativeIOtlOl'l is subject to frictional damping in order to preventdetrimental oscillatory or hunting effects.

In order to achieve these objects we design an electric contactor inaccordance with the principles elucidated hereinafter with reference tothe drawing, in which:

Figure 1 is a sectional top view of a switching apparatus according tothe invention, the section being taken along the radial plane denoted inFig. 2 by 1-1, and

Fig. 2 is an axial section through the same apparatus taken along thedihedral cut denoted in Fig. 1 by II-II,

The apparatus illustrated in the drawing is provided with a casing Iwhich forms the supporting structure for the other parts and is pl videdat one side with a mounting flange The other side of easing is closed bya cover plate 3. A shaft 4 is revolvably mounted by means of ballbearings 5 and 6 in the flange portion and cover plate, respectively.The cover plate 3 carries an insulatin block 7 which supports threeterminals 8, 9 and it, each forming a holder for a contact brush H, !2and i3, respectively.

A hub M is keyed to shaft 4 and carries a disk E5 of insulatingmaterial. This disk is provided with an annular insulator !6. Three sliprings l7, l8 and I9 are mounted on the insulator it for engagement bythe contact brushes 5 i, 2 and I3, respectively. Disk I5 is furtherequipped with a support 20 for two leaf spring contacts 2! and 22, Twofurther supports denoted by 23 and 24 are also mounted on disk 15 andcarry two leaf spring contacts 25 and 2b, respectively. The four leafspring contacts extend substantially in axial planes relative to therotation of shaft 4, and con tacts 2i and 22 are axially spaced from thecorresponding contacts 25 and 26, respectively. Contacts 2! and 22 areelectrically connected with one of the slip rings, while contacts 25 and26 are in connection with the remaining two slip rings, respectively.

The insulating disk l5 carries further a support 28 for an adjustablestop or calibrating mechanism which comprises a finger 29, a helicalcompression spring 38 and an adjusting screw 3|. One end of finger 29rests normally against the support 28 and abuts against a projection ofthe support so as to be capable of pivotal motion in opposition to thebiasing force of spring 30. This force can be adjusted by means of screw3|. The other end of finger 29 is bent to an angular shape.

Another support 33 also mounted on disk l5 carries a finger 34, ahelical compression spring 35 and an adjusting screw 35. One end offinger 34 is pivoted on support 33 while the other end, denoted by ill,is of angular shape. Support 33 and the parts attached thereto form asecond stop or calibrating mechanism arranged symmetrically to the onedescribed in the foregoing.

A flywheel 38 is revolvably mounted on shaft 4 by means of ball bearings39 and cc. Two drive pins 4! and #2 project from flywheel 38 toward disk#5 and enter freely into elongated openings of disk 95, such as theopening denoted by 33 in Fig. 2. The above-mentioned angular ends 32 and37 of fingers 29 and 34 are so located relative to pins 4! and 42,respectively, that each finger is normally in contact engagement withthe adjacent pin. The contact surfaces of finger ends 32 and 37 extendat an angle to the radius which passes through the point of engagementbetween fin er and appertaining drive pin. Flyative to disk l5. wheel.38 is normally held in a given position rel- Two supports 8 and 44,respectively, are firmly attached to the flywheel and carry each abarshaped and slotted bridging contact 45 and 46, respectively,consisting of silver or the like highly conductive material. Thebridging contacts are located so that they enter between the adjacentpair of contact springs 2! and 25, or 22 and 26 when the flywheelrotates relative to disk I5.

It will be recognized from the foregoing that the shaft t with its hubl5 and the insulating disk 3 I5 with all parts attached thereto form adrivable member while the flywheel 38 and the appertaim'ng partsrepresent a floating member. The squared or flattened end c1 of shaft tserves to connect the drivable member with a rotating machine part whoseacceleration or deceleration is intended to control the switchingperformance. When the. driven member is rotating at constant speed, thetwo stop mechanisms described in the foregoing hold the floatingflywheel in midposiacceleration increases beyond the limit value,

the stop mechanism will yield so that one of the contact bars 35 or 36enters between the adjacent pair of leaf spring contacts and closes acontrol circuit between two of the-contact terminals of the apparatus.

When the driven assembly decelerates, the same performance is obtained,except that now the other stop mechanism is operative so that the othercontact bar closes a circuit between the appertaining two leaf springcontacts. In this .manner, an electrical control function can beperformed by the apparatus in dependence upon the'occurrence ofpredetermined rates of accel- -eration and deceleration.

As explained in the foregoing, the two adjustable -stop mechanismsoperate independently of each other, one being active in response toacceleration and the other responsive to deceleration. That is, only oneof the two resilient stops here represented by the contact fingers 29and 3 1 is in operation at a time. This has the advantage that thebiasing force of each stop can be changed or calibrated independent ofthe other stop mechianism. Hence, the apparatus can be made to respondto one rate of acceleration and to another rate of deceleration, 01' itpermits a very accurate-calibration of the two stop mechanisms if theyare to become effective at the same rate of speed change regardless ofthe direction of the change.

Due to the fact that the contact surface of .each finger 29 and 3% liesat an angle to the radius of rotationwlth reference to the point ofengagement between finger and appertaining drive pin, any relativemotion between the driven member and the floating member will cause thecontactsurface of the yielding finger to drag along the pin. Thissliding motion produces friction which tends to dampen any oscillationapt to occur at sudden changes in rate of speed.

.The ends of the contact-bars and are wedgeshaped, so that they enterbetween the adjacent .spring contacts with aminimum increase in effort.

This-construction has further the-advantage that it provides a doublebreak in the circuit. The friction occurring between the contact bar andthe leaf springs provides additional-sliding friction which assists inthe suppression of undesirable-oscillations. The sloping approach on thebridging contact has the advantage over a straight contact that contactpressure and friction decrease when the bar, under the biasing effect ofthe stop mechanisms, withdraws from the relative motion occurringbctweensaid the leaf spring contacts. This reduces the tendency of the contactsto stay closed at reduced rates of change in speed and, therefore,reduces the difference between the pickup and dropout rating of theswitch. Another advantage of the contact structure is the fact that noflexible shunts are required.

The'elongated holesof the disk'lisuch as the hole denoted by 43 in Fig.2, co-operate with the ends of the pins 4| and 42 in preventing anexcessive deflection of the calibrating springs 3i] and 35. The pins arenormally out of engagement with the edges of the holes, except when therelative motion between driven member and floatingmember is far inexcess of the normally expected deflection. This allows freedom ofmovement over the required range but prevents detrimental overtravel.

Apparatus according to the invention are of advantage in control orregulating arrangements in which an electric control function is to beperformed in dependence upon the occurrence of a given rate of speedchange, or in cases where a machine is supposed to accelerate ordecelerate at a high rate which, however, is intended not to exceed sucha value as to incur -mechanical or electrical overloads. It will beunderstood that when only an acceleration responsive or only adecelerationresponsive control is required, only one of the stopmechanisms need be adjustable. It will also be obvious to those skilledin the art that various other modifications can be applied within thegist of ourinvention and without departing from the essential featuresof the invention as set forth in the claims annexed hereto.

We claim as our invention:

1. An electric control device comprising a rotatable drivable member, afloating mass'member coaxially rotatable relative to said drivable her,an adjustable spring device for imposing on said members a bias ofselective magnitude for causing them to normally maintain agiven angularposition relativeto each other, and iectric contact means having twoco-cperative parts mounted on said two members respec lvely so as toperform a switching operation in response to two members when the rateof speed change of said drivable member exceeds a value determined bythese-lected adjustmentof saidspring device.

2. An electric switch comprising a rotatable drivable member, a floatingmass member coaxially rotatable relative to said drivable member, aresilient stop mechanism disposed between said twormembers for biasingthem inone direction of relative rotation toward a position of restrelative to each other, an adjustable resilient stop mechanism alsodisposed between said two membersfor biasing them in the other directiontolard said position of rest, and-electric contact means having twoco-operative parts mounted on said two members respectively so as toperform a rounding said pin for limiting the relative rotation of saidmembers, and a calibratng mechanism mounted on said other member andhaving a resilient stop engaging said pin for biasing it in onedirection or said relative rotation toward a position of rest relativeto said one member, and electric contact means having two co-operativeparts mounted on said two members respectively so a to v erform aswitching operation in response to the relative motion occurring betweensaid two members when the rate of speed change of said drivable memberexceeds a value determined by the calibration of said mechanism.

4. An electric switch comprising a rotatable drivable member, a floatingmass member coaxially rotatable relative to said drivable member, one ofsaid members having a pin extending substantially in parallel to theaxis of rotation and the other member having a resilient stop engagingsaid pin, said stop having an engaging surface extending at an angle tothe radius of rotation at the point of engagement whereby frictionalsliding motion is caused between surface and pin when said two membersrotate relative to each other, and electric contact means having twocooperative parts mounted on said two members respectively so as toperform a switching operation in response to the relative motionoccurring between said two members when the rate of speed change of saiddrivable member exceeds a given v value.

5. An electric switch comprising a rotatable drivable member, a floatingmass member coaxially rotatable relative to said drivable member,

biasing means disposed between said members for causing them to normallyassume a given angular position relative to each other, two insulatedcontacts resiliently mounted on one of said members in axially spacedrelationship, and a bridging contact mounted on said other member so asto enter between and electrically bridge said spaced contacts underfrictional sliding motion when said two members rotate relatively toeach other due to the occurrence of an excessive rate of change in speedof said drivable member.

6. An electric switch comprising a rotatable drivable member, a floatingmass member coaxially rotatable relative to said drivable member andhaving a pin extending substantially in parallel to the axis ofrotation, said drivable member having a resilient stop for engaging saidpin, said stop comprising a rigid support, a finger having one endpivoted on said support and the other end bent so as to form a surfacefor contacting said pin at an angle to the radius of rotation at thepoint of contact, a spring for biasing said pivoted finger end towardsaid support, and an adjusting screw for adjusting the biasing force ofsaid spring, and electric contact means having two co-operative partsmounted on said two members respectively so as to perform a switchingoperation in response to the relative motion occurring between said twomembers when the rate of speed change of said drivable member exceeds avalue determined by the setting of said adjusting screw.

MAURICE F. JONES. RUEL C. JONES.

